1. Field of the Invention
The present invention relates generally to light guide panels and backlight modules using the same, and more particularly to a light guide panel for liquid crystal display (LCD) devices and a backlight module using the light guide panel.
2. Description of the Prior Art
LCD devices have been used extensively in liquid crystal televisions (LCTVs), computers, cell phones and personal digital assistants (PDAs). Due to the ever increasing size and the product standard keeps enhancing, for LCD devices having advantages such as lightweight, low power consumption and low radiation, the market boundary for these devices keeps expanding. The backlight module is one of the important elements in LCD devices. Since liquid crystal materials in the LCD devices are not self luminous, the backlight modules are needed to provide light and to achieve display effect. As the application level of various panel dimensions of the LCD devices keep expanding, the backlight module industry has been on an upward trend over a long period or time. Especially, the market demand for LCD devices in recent years has increased considerably. In order to accord with functional and outward appearance requirements of the LCD devices, the backlight module design for LCD devices has gradually become multidimensional.
A backlight module mainly comprises a light guide plate, a light source module, a reflector and one to a plurality of optical films. In order to achieve design objectives of backlight modules, such as low power, high brightness, uniform luminosity and controllable view angle, the optical elements within the backlight module use various optical designs to enhance light utilization efficiency. The primary function of a light guide plate is to guide the light path and to achieve uniform brightness. Due to the fact that the refractive index of a light guide plate is greater than ambient atmosphere, light paths within the light guide plate travel mostly by way of total reflection. In addition, a plurality of microstructures is disposed on part of the bottom surface or top surface of the light guide plate to enhance overall light output uniformity and luminance.
FIG. 1 shows a conventional backlight module. As shown in FIG. 1, the backlight module comprises a light guide plate 80, a light source module 40, a light source diffusion module 60 and a reflector 20. The light source module 40 is disposed on the lateral side of the light guide plate 80, the reflector 20 is disposed under the light guide plate 80, and the light source diffusion module 60 is disposed above the light guide plate 80. A plurality of microstructures 83 is disposed on a bottom surface 81 of the light guide plate 80. The microstructures 83 are V-shaped grooves, and pointy ends 85 are formed between the two grooves. As shown in FIG. 1, the bottom surface 81 of the light guide plate 80 and the reflector 20 are superimposed, and the pointy ends 85 touch against the reflector 20.
In the conventional backlight module design in FIG. 1, the microstructures 83 on the light guide plate 80 contact directly with the reflector 20. However, the contact between the microstructures 83 and the reflector 20 frequently damages the microstructures 83 and the reflector 20. For example, abrasion between the microstructures 83 and the reflector 20 caused by transport, vibration tests or other relative movements results in scrapes on the microstructures 83, and further white spots, luminance streaks (mura) and poor pervious to light on LCD panel. The scrape issue of the microstructures may cause the loss of optical characteristics of the light guide plate, disable it to reach the intended performance, result in a defective product, and even the overall production yield of the backlight module is reduced and the cost of production is increased. Accordingly, how to protect the light guide plate and the optical elements next to the light guide plate from scrape and abrasion has posed a major challenge to the backlight module design.
FIG. 2 shows an improved structure of a conventional backlight module. As shown in FIG. 2, the backlight module comprises a light guide plate 90, a light source module 30, a light source diffusion module 50 and a reflector 10. The light source module 30 is disposed on the lateral side of the light guide plate 90, the reflector 10 is disposed under the light guide plate 90, and the light source diffusion module 50 is disposed above the light guide plate 90. A plurality of microstructures 93 is disposed on a bottom surface 91 of the light guide plate 90. The microstructures 93 are V-shaped grooves, and plane surfaces are between the two grooves. As shown in FIG. 2, the bottom surface 91 of the light guide plate 90 is superimposed with the reflector 10, and the plane surfaces 95 touch against the reflector 10.
The improved structure eliminates the contact issue of pointy ends of the microstructures in the conventional backlight module, and planar contact is utilized to distribute the concentration of force, thus the contact abrasion between the microstructures 93 and the reflector 10 is reduced, and scrape and abrasion occurrences of the light guide plate 90 is reduced as well. However, the microstructures 93 and the reflector 10 still have a fairly large surface contact in this improved structure. Although the plane surfaces 95 touching against the reflector 10 help reduce the abrasion degree of the microstructures 93, the planar surface contact between the plane surfaces 95 and the reflector 10 may still create scrape and abrasion issues.